Actually Gobnait (probably a feminine diminutive of goba 'smith', from the Celtic god of craftmanship, Gobniu, an important Munster saint, Munster is where it survives best today) was often Anglicised as Abbie or Abigail but the reasons behind this aren't clear. The best theory I've heard is that a small female 'smith' would be about equivalent to an Abigail which was once a term for a maid, doubtless because the Biblical Abigail refers to herself as 'thy servant'. It became a common reference and literature and plays from the Middle Ages up to the 1800's often featured maids named Abigail, encouraging it's use as a slang term for a maid, the way we describe 'clients' of prostitutes as 'Johns'. No telling if that's the real reason or not, it's simply one that has surface logic to it.